There was a telling moment during the recent Democratic presidential debate in Austin. Hillary Clinton made a sarcastic remark about the pseudo-scandal involving whether Barack Obama had borrowed a few lines of rhetoric from Massachusetts Gov. Deval Patrick, and in response the audience booed her. They didn't think the crack was fair, and they let Clinton know it.

The moral is that, in politics, even if you believe an attack on an opponent is justified, you should think twice about launching it, because it can backfire.

Clinton would be wise to keep that in mind as she ratchets up her attempts to stop Obama's momentum by going negative. Well, more negative than usual, that is.

Behind in delegates, having trouble in fundraising, stinging from 11 straight losses, the Clinton campaign is pursuing five separate lines of attack at once as part of what one adviser said was a "kitchen sink" strategy aimed at convincing voters that Obama is too big a risk.

There's the accusation that Obama is a lightweight on foreign policy; the charge that he has distorted Clinton's views on the North American Free Trade Agreement; the claim that he is naive and idealistic; and the insistence that he won't distance himself from outside groups spending money on advertising on his behalf. The final item may or may not be coming from the Clinton campaign, but it sure came from somewhere - the release of a photo of Barack Obama in ceremonial dress, including a turban, on a visit to Africa.

In this week's debate in Cleveland, Clinton denied that the photo had come from someone in her campaign, as some have claimed. But, since her last name is Clinton, she is smart enough to build an escape hatch. The photo wasn't leaked by her campaign "so far as I know," she said.

Regardless of who leaked the photo, you can be sure why it was leaked. This is nothing more than a cheap trick intended to advance the notion that, somehow, Obama - because of his name, heritage or life story - isn't a true American. Flirting with bigotry and nativism is the lowest form of political discourse. It's a shame that the race for the Democratic nomination for president has come to this.

Time and again, voters have shown by both word and deed that they don't like these kinds of personal attacks. And when these attacks come in the eleventh hour, voters are even more likely to consider them acts of desperation. And then they really dislike them.

Clinton is obviously playing to win, but she is also playing with fire. If she really believes she would be a better president than Obama, then let her keep trying to make her case to voters. But by relentlessly attacking her opponent, over matters large and small, she only makes herself appear more unlikable and less electable.

Those are never good things in politics, and especially not when you're already losing the popularity contest.